This invention relates in general to electrical connectors and, more specifically, to latchable electrical connectors that are resistant to inadvertent separation and impact or crushing damage.
A wide variety of electrical connectors have been developed to connect electrical cables together, to connect cables to equipment, etc. Several standard connectors have been developed for use with different voltage and current levels. Typically, these have several differently shaped and spaced prongs on one component that slip into correspondingly configured sockets on a second component. While effective in normal household use, these are less than fully effective in many applications and environments.
Where extensive use of extension cables is required, such as in the construction industry, in lighting motion picture or video sets, etc., connectors may be subject to forces tending to pull them apart and to environmental conditions that can contaminate the connector or prongs with water or other materials. Also, these connectors are subject to damage to prongs when disconnected, such as by having prongs bent or damaged by persons stepping on them, being run over by vehicles and the like. When the prongs are contaminated, or where the connector is not fully connected, intermittent short circuits between prongs or intermittent open circuits may occur, which are often very difficult to detect and repair. Further, partially inserted prongs may allow the circuit to function, but may allow metallic contamination to touch the prongs causing short circuits or even fires. There is even a possibility of electrocution where a person handling cables comes into contact with prongs that are not fully inserted, particularly on outdoor, possibly wet, construction sites or the like.
Attempts are made to reduce these problems and dangers by knotting the cables together adjacent to the connection or apply clamping devices to hold the connection together. Knotted cables are cumbersome and provide projections over which people may trip and stumble. The clamps, while sometimes effective, are also large and cumbersome an capable of failure if not properly used.
Many connectors are hollow and relatively fragile and subject to damage if subjected to impact or crushing, such as when construction material is dropped on a connector or it is run over by a vehicle.
A number of special connectors have been developed in attempts to overcome these problems. For example, Armstrong et al. in U.S. Pat. No. 3,984,169 disclose a complex keying arrangement in which one component is pivoted about a swivel pin to bring a coded arrangement of blades and slots into mesh to connect a cable to a power distribution panel. A separate latch mechanism is required to keep the unit connected. While useful in this special application, this arrangement has little utility in normal cable to cable or cable to outlet connections.
Meile in U.S. Pat. No. 3,171,704 discloses an electrical connector made up of a first hollow box having a concave surface at one end on which several electrical contacts are formed and a second hollow box having a thin extended finger having a convex surface corresponding to the concave first surface, with three complementary contacts on the convex surface. These two surface are pivoted into contact about a pin to make a connection that cannot be separated by a straight line pull. While effective for many purposes, this connector is undesirably fragile for use in difficult environments. For example, the boxes will be subject to breaking, cracking or crushing if stepped upon or run over be vehicles with hard wheels. The thin sleeve that covers the unit when assembled may crack and expose the pivoting hooks that are part of the conductor system. The thin convex conductor member is liable to bend or break, causing at least intermittent loss of continuity and possible danger when used in a hazardous atmosphere.
Thus, there is a continuing need for improved electrical connectors for use in circumstances such as where a number of connected cables are connected across floors or roadways, such as in construction, lighting, or in emergency applications such as natural disaster relief work. Connectors are necessary that cannot be separated by straight line pull, and will not be damaged or cause electrical hazards when subjected to abuse.